ACL and metaData handling improved

ACL and metadata handling has been improved.

You can now save file like this:
```groovy
file.save(CloudFileACL.PublicRead)
// Or
file.save(CloudFileACL.Private) // Default on S3
```

This update will require the changes made in `karman` pull request for ACL handling.
Once you have released a new version of it, please update the dependencies:
```groovy
runtime ':karman:0.2.0-SNAPSHOT'
// To
runtime ':karman:0.2.0'
```

I've also renamed the package to `com.bertramlabs.plugins.karman.aws`, which sound more logical when compared to `com.bertramlabs.plugins.karman.local` package.
Is it OK?